The present invention generally pertains to the radio transmission field and, more precisely, point-to-point radio communication system with frequency reuse techniques. Still more in particular, it concerns a method and device for realizing the carrier synchronization when, in addition to the cross-polar signal, one desires to cancel other (one or more) co-channel signals: (whether they are co-polar or cross-polar).
Within the telecommunication systems using microwave radio relay systems of the point-to-point type as a transmitting equipment, there is a constant need to increase as far as possible the spectral efficiency, i.e. the amount of information transmitted per unit of occupied band. An answer to this need is obtained through the frequency reuse: this is a solid technique by now which consists in transmitting simultaneously on the same frequency two different signals on two orthogonal polarizations (for instance on H polarization and on V polarization). Because of the non-ideal nature of the transmitting equipment and medium, the two signals are subjected to mutual interference which can also be of such a level as to make the received signal no longer intelligible.
It is known that through the use of a canceller (hereinafter XPIC) it is possible, at least in principle, to completely eliminate, in reception, the interference of V on H and similarly of H on V (see the basic diagram reproduced in FIG. 1).
Further to the above described problem (increase in the spectral efficiency), in the implementation of telecommunication networks through radio relay systems, one of the biggest problems encountered is concerned with the position of sites, i.e. of the place where to position the (transmit and receive) antennas and the related (transmit and receive) equipment.
Often it happens that, due to orographic, topological needs or yet to needs related to the installation costs, the position of a site cannot be arbitrarily changeable but it is bound; in these circumstances it happens that the site is “crowded” i.e. that several antennas are already present for transmitting and receiving several signals, also isofrequential with the one which it is wished to be transmitted, i.e. co-channel signals.